fix more build errors

auctionsim/summary.go

@@ -0,0 +1,139 @@
+package auctionsim
+
+import (
+	"math"
+	"strconv"
+)
+
+// Digits of precision in floating-point values in CSVs.
+const CSVPrecision = 10
+
+/**
+ * ResultSummary contains notable results of an auction.
+ */
+type ResultSummary struct {
+	/// The number of bidders in the auction.
+	Bidders int
+	/// The price the item sold for.
+	Price float64
+	/// The amount of value the winner actually got out of the auctioned item.
+	WinnerValue float64
+	/// The highest bid the auction winner was willing to make.
+	WinnerMaxBid float64
+	/**
+	 * The amount by which the winner's value of the item exceeded the price
+	 * they paid. Often negative.
+	 */
+	WinnerProfit float64
+	/**
+	 * Number of losing bidders who had a "true value" of the item in excess
+	 * of the price paid.
+	 */
+	LosersWithRegrets int
+	/// The most the item was genuinely worth to any bidder.
+	HighestValue float64
+	/// The most the bidder with the highest value would have been willing to pay.
+	HighestValuatorBid float64
+	/**
+	 * How much the bidder with the highest value would have made in profit had
+	 * they won the auction for the price the auction's actual winner paid.
+	 * Often negative, indicating nobody would have made money on the auction.
+	 * If this is zero or negative, there are 0 losers with regrets.
+	 */
+	MissedProfit float64
+	/**
+	 * How much more valuable the item was to the bidder with the highest value
+	 * than it was to the auction's eventual winner, irrespective of winning bid.
+	 */
+	ValueDelta float64
+	/**
+	 * The rank of the bidder who actually had the highest value of the item.
+	 * The winner of the auction has rank 1. If all bidders had a true value of
+	 * negative infinity for the item, this will be greater than the number of
+	 * bidders.
+	 */
+	HighestValueRank int
+}
+
+/**
+ * Summarize takes an already-sorted list of bidders (see RunAuctionVerbosely)
+ * and the winning auction price, and calculates a ResultSummary for that auction.
+ */
+func Summarize(price float64, allBidders []Bidder) *ResultSummary {
+	regrets := 0
+	maxValue := math.Inf(-1)
+	maxIdx := -1
+
+	for i, b := range allBidders {
+		if b.Value > maxValue {
+			maxValue = b.Value
+			maxIdx = i
+		}
+		if b.Value > price {
+			regrets++
+		}
+	}
+
+	winner := allBidders[len(allBidders)-1]
+	rube := Bidder{Value: math.Inf(-1)}
+	if maxIdx >= 0 {
+		rube = allBidders[maxIdx]
+	}
+	return &ResultSummary{
+		Bidders:            len(allBidders),
+		Price:              price,
+		WinnerValue:        winner.Value,
+		WinnerMaxBid:       winner.BidCeiling(),
+		WinnerProfit:       winner.Value - price,
+		LosersWithRegrets:  regrets,
+		HighestValue:       maxValue,
+		HighestValuatorBid: rube.BidCeiling(),
+		MissedProfit:       rube.Value - price,
+		ValueDelta:         maxValue - winner.Value,
+		HighestValueRank:   len(allBidders) - maxIdx,
+	}
+}
+
+/**
+ * ResultSummaryCSVHeader returns column labels for the records emitted by
+ * (*ResultSummary).CSVRecord().
+ */
+func ResultSummaryCSVHeader() []string {
+	return []string{
+		"Bidders",
+		"Price",
+		"WinnerValue",
+		"WinnerMaxBid",
+		"WinnerProfit",
+		"LosersWithRegrets",
+		"HighestValue",
+		"HighestValuatorBid",
+		"MissedProfit",
+		"ValueDelta",
+		"HighestValueRank",
+	}
+}
+
+func csvFloat(f float64) string {
+	return strconv.FormatFloat(f, 'g', CSVPrecision, 64)
+}
+
+/**
+ * CSVRecord returns rows intended for use with encoding/csv.Writer, with
+ * columns in the order specified by ResultSummaryCSVHeader().
+ */
+func (s *ResultSummary) CSVRecord() []string {
+	return []string{
+		strconv.Itoa(s.Bidders),
+		csvFloat(s.Price),
+		csvFloat(s.WinnerValue),
+		csvFloat(s.WinnerMaxBid),
+		csvFloat(s.WinnerProfit),
+		strconv.Itoa(s.LosersWithRegrets),
+		csvFloat(s.HighestValue),
+		csvFloat(s.HighestValuatorBid),
+		csvFloat(s.MissedProfit),
+		csvFloat(s.ValueDelta),
+		strconv.Itoa(s.HighestValueRank),
+	}
+}

main/main.go

@@ -4,7 +4,6 @@ import (
 	"fmt"
 	"git.chromaticdragon.app/kistaro/auctionsim/auctionsim"
 	"log"
-	"math"
 	"os"
 	"strconv"
 )
@@ -32,54 +31,30 @@ func main() {
 		log.Fatalf("can't run an auction with %d bidders", num)
 	}
 
-	price, allBidders := auctionsim.RunAuctionVerbosely(
+	summary := auctionsim.Summarize(auctionsim.RunAuctionVerbosely(
 		&auctionsim.CappedBidderGenerator{
 			G:   auctionsim.NormalestBidderGenerator(),
 			Lim: num,
 		},
-	)
-	bidder := allBidders[len(allBidders)-1]
-
-	fmt.Printf("The auction winner paid ¤%f. They have %s.\n", price, deltaStr(bidder.Value-price))
-	fmt.Printf("The item was worth ¤%f to them.\n", bidder.Value)
-	fmt.Printf("They would have paid up to ¤%f for it.\n", bidder.BidCeiling())
+	))
+	fmt.Printf("The auction winner paid ¤%f. They have %s.\n", summary.Price, deltaStr(summary.WinnerProfit))
+	fmt.Printf("The item was worth ¤%f to them.\n", summary.WinnerValue)
+	fmt.Printf("They would have paid up to ¤%f for it.\n", summary.WinnerMaxBid)
 
 	fmt.Println()
-	i := len(allBidders) - 2
-	for i >= 0 && allBidders[i].Value < price {
-		i--
-	}
-
-	if i < 0 {
-		fmt.Printf("The item was not worth that to anybody.\n")
+	if summary.LosersWithRegrets < 1 {
+		fmt.Println("The item was not worth that to anybody.")
 	} else {
-		rube := allBidders[i]
-		fmt.Printf("The highest bidder who would have made a profit at that price stopped bidding at ¤%f.\n", rube.BidCeiling())
-		fmt.Printf("They should have kept bidding until ¤%f.\n", rube.Value)
-		if rankDelta := len(allBidders) - i - 1; rankDelta == 1 {
-			fmt.Println("They were outbid by 1 bidder.")
-		} else {
-			fmt.Printf("They were outbid by %d bidders.\n", rankDelta)
-		}
-		fmt.Printf("If they had paid the amount of the winning bid, they would have %s.\n", deltaStr(rube.Value-price))
+		fmt.Printf("The item was worth that to %d bidders, who stopped bidding too soon.\n", summary.LosersWithRegrets)
 	}
 
 	fmt.Println()
-	maxValue := math.Inf(-1)
-	maxIdx := -1
-	for i, b := range allBidders {
-		if b.Value > maxValue {
-			maxValue = b.Value
-			maxIdx = i
-		}
-	}
-
-	if maxIdx == -1 {
+	if summary.HighestValueRank > summary.Bidders {
 		fmt.Println("Wow! It was infinitely beyond worthless to everybody.")
 	} else {
-		fmt.Printf("The bidder who would have gotten the most value was outbid by %d bidders.\n", len(allBidders)-maxIdx-1)
-		rube := allBidders[maxIdx]
-		fmt.Printf("The item was worth at most ¤%f to them. Their maximum bid was ¤%f.\n", rube.Value, rube.BidCeiling())
-		fmt.Printf("If they had paid the winning bid, they would have %s.\n", deltaStr(rube.Value-price))
+		fmt.Printf("The bidder who would have gotten the most value was outbid by %d bidders.\n", summary.HighestValueRank-1)
+		fmt.Printf("The item was worth at most ¤%f to them. Their maximum bid was ¤%f.\n", summary.HighestValue, summary.HighestValuatorBid)
+		fmt.Printf("If they had paid the winning bid, they would have %s.\n", deltaStr(summary.MissedProfit))
+		fmt.Printf("They valued it ¤%f more than the winning bidder.\n", summary.ValueDelta)
 	}
 }